Sulfur recovery apparatus



Patented Nov.- 11,1952

V SULFUR RECOVERY APPARATUS Charles A. Porter, Chicago, and Milton M. Marisic,

N orthbrook, 111., assignors to The Pure Oil Company, Chicago, Ill., a corporation of Ohio Original application April 21, 1945, Serial No.

589,679. Divided and this application September 23, 1947, Serial No. 775,628

2 Claims. 1

This invention relates to'method and apparatus for vaporizingand superheating sulfur.

This application is a division of our application Serial Number 589,679, filed April 21, 1945, now Patent N0. 2,508,292, issued May 16, 1950.

vaporization of sulfur and superheating of sulfur vapors are two of the most difiicult problems encountered in chemical operations. Sulfur ordinarily contains a small amount of both organic and inorganic impurities which deposit on the vaporizing surfaces when sulfur is vaporized causing formation of coke and. scale deposits which necessitate frequent cleaning of the still in order to obtain satisfactory heat transfer rates without exceeding safe metal temperatures. 'In superheating sulfur vapors the principal difliculty is encountered in the corrosive effect of sulfur on all common metals and alloys at elevated temperature. Not only is the life of the heating element shortened, but scale formation on the surface of the heating elements greatly reduces the heating transfer rates. Many chemical syntheses involving use of sulfur would be possible if a satisfactory method and apparatus for vaporizing and-superheating sulfur was available.

An object of this invention is to provide an apparatus for vaporizing sulfur,

A further object of the invention is to provide a method and apparatus for superheating sulfur vapors without any substantial corrosion of the apparatus. a

Further objects of this invention will manifest themselves from the following description and the accompanying drawings, of which Figure 1 is a diagrammatic elevational view of one form of apparauts for carrying out the invention; and Figure 2 a diagrammatic elevational view of another form of apparatus for carrying out the invention.

Referring to Figure 1,.the numeral I designates a pump by means of which molten sulfur at a temperature between approximately 250 and 300 F. is pumped through line 2 into vaporizing and superheating column'or chamber 3. Column 3 is lined with refractory material such as carborundum, alundum, quartz, fire brick, or the use, which is not attacked by sulfur to any substantial extent. Column 3 is filled with a bed of pelleted, fragmentary or granular refractory ma terial such as carborundum, alundum, quartz or fire brick, heated to a temperature somewhat above the temperature to which it is desired to superheat sulfur vapors. Upon contact of the molten sulfur withthe movingbed of refractory material the sulfur is vaporized and passes 'upward through the bed in direct heat exchange with the hot refractory material and becomes heated to the desired temperature. The superheated sulfur vapors leave the top of chamber 3 through line 4 and are charged to a system in which it is desired to use the superheated sulfur vapors, such as for example a reactor for making carbon disulfide by reaction of superheated sulfur vapors with methane, or other hydrocarbon gases, in the presence of a suitable catalyst such as silica gel, activated alumina, activated clai or synthetic silica-alumina catalyst. The molten sulfur enters the chamber 3 preferably some distance from; the bottom thereof but below t he middle; of the co u -m v superheated steam is admitted to the bottom of the column 3 through valve-controlledpipe 5 at .a temperature of approximately 900-950 F, in

order to purge residual sulfur from the refractory material. An outlet 6 is provided between the line 5 and line 2 for drawing off the steam and sulfur vapors contained therein from the purged refractory material. The line 6 is connected to a condenser 1 maintained under atmospheric or superatmospheric pressure. Water, steam and sulfur in molten form pass from; the condenser 1 to the receiver 8. Suflicient pressure may be maintained in the condenser and receiver 8 so that substantially all the steam and sulfur is condensed to liquid or molten state. Pressure in the column 3 will be somewhat above that maintained inthe condenser 1 so that the purging steam and sulfur vapors contained therein will pass through line 6 instead of passing upward through the column 3 to the outlet 4. It will be understood, of course, that a certain portion of the purging steam will pass upward through column 3 and be eliminated through line 4, From the receiver 8 molten sulfur is recycled through line 9 by means of pump l 0 through line I I controlled by valve l2to line 2. Hot water and steam are withdrawn from the upper" portion of receiver 8 through valve-controlled line 13.

- Hot refractory material is intermittently intro duced into the vaporizer and superheater 3 from hopperl 4- through line {5 controlled by valve 16. The refractory material is intermittently withdrawn from the bottom of column 3 through-line I 1 controlled by valve l1 and passes to hopper [8; At such time as hopper I4 is being emptied into column 3, valve IS in the outlet of hopper- I 8, and valve 20 in the inlet to hopper M are closed. Refractory material is preferably withdrawn from column;3.into: cppe r l 8 atthe. same time as hop:

per ligislemptied in column s. When'hqpper 1M fractory material from hopper i8 is discharged therefrom through valve l8 and the refractory material passes into receiver 22.

During the time that steam is withdrawn from the hopper I8 hopper I4 is depressed and sulfur is withdrawn therefrom through valve-controlled line 23. The sulfur vapors may be condensed and recycled to line 2 through a line not'shown. Valve is then opened and hopper HI is then recharged with hot refractory material from receiver 24 through valve 20. As soon ashopper I4 is filled with hot refractory material valve is closed and any flue gas which may have accumulated in hopper I4 is exhausted therefrom through valve-controlled "line 23. Hopper "I4 "is then pressured with sulfur vapors from line '4 by opening valve 25in line 25 and permitting sulfur'vaporsto'ilow into the hopper l4. When the pressure between chamber 3 and hopper 1'4 has been equalized valve '16 is again opened and "the refractory material is permitted to flow from the hopper I4 into top-of chamber Sand valve 11 is opened to permit refractory material to 'be withdrawn from the bottom of chamber "3.

From the receiver 22 granular refractory material passes continuouslythrou'gh' line "2-1 "to elevator 28, which may be of 'thebucket, or any other suitable type, and is conveyed to kiln'ZS through line 36. The refractory material passes downwardly through kiln 25 and is heated during itsdownward passage to the desired "temperature "by burning in the kiln combustible gases mixed with air charged thereto through manifold 3| and valve-controlled lines '32, 33, 34, 35, and-3B at spaced points along the kiln. Any suitable liquid, powdered or gaseous fuel maybe burned in the kiln 29 such as natural or producer gas, furnac oil, acid sludge, or tar. Ap'ortion of the 'heat may be supplied by combustion of organic matte deposited on the refractory =ma- "terial during the sulfur vaporization step. Some "crude sulfurs contain substantial amounts of organic matter which is separated during the vaporization and superheating step and leftdeposited.in'the.'form of coke on the refractory material. This organic matter is burned from the refractory material in 'kiln 2'9 by supplying su'fiicient excess of airtoburn the organic matter.

Flue gases leave the kiln 29 through valvecontrolled lines 31, 38,435, 45 and 4|. The heated refractory material leaves the bottom of the kilnthrough line 42 controlled "by valve Band is carried by e1evat'or 4'4 to line 45 which empties into "the top of receiver 24. Any residual flue gas in the heated refractory material is withdrawn from receiver 2'41 through valve-controlled line 45. r

In the apparatus jus't described, in addition to the vapor'izing and superheating chamber 3, hoppers l4 and i8 are preferably lined with refractory material, as well as such other ortions of theapparatus which come in direct contact with sulfur vapors .at high temperature.

Instead of purging the refractory material by injecting superheated steam through line 5 into the bottom of chamber 3 and withdrawing the steam and contained sulfur vapor through'line ii, th refractory material may :be purged in hopper l8 by injecting superheated steam into the bottom thereof through valve-controlled line 41 and withdrawing the steam with its sulfur content from the top of hopper 18 through valve-controlled line 48 which, in turn connects to line 6.

It will be apparent that the apparatus shown in Figure 1 may be used to purify contaminated sulfur. In such case the refractory material will be heated to a temperature suificient only to vaporize the sulfur. Such temperature may be approximately 1000 to 1100 F.

Referring now to Figure 2, solid sulfur in small pieces or in powdered state is fed from hopper 50 through valve 5| by means of screw conveyor to a sulfur melter 53. The sulfur is melted in melter '53 by direct contact with superheated steam or hot water under pressure. Sulfur is charged to the melter 53 intermittently. When the melter is filled with sulfur, valve 5| is closed and superheated steam'is introduced into the bottom of melter 53 through valve controlled line 54. Meltedsulfurand water are transferred from the bottom of melter 5-3 through line 55 controlled by valve 56 to a sulfur-water "separator 51. Valve 55 is then closed and melter '53 depressurized by opening valve on lin 51' on the top of the melter to permit steam to escape and is then recharged by opening valve '51 and "operating screw conveyer 52. Sincemelter 53 is operated intermittently it should be made sufficiently large to provide a suificient supply of molten sulfur for separator 5'! so as to enable sulfur vaporizing and superheating operation to be carried oncontlnuously.

Water is removed from the top of separator S'Ithrough valve-controlled line 58, Molten sulfur-at a' temperature of approximately 250-275 F. is withdrawn from 'thebottom of separator 51 through line 59 by means of pump to and pumped through'line 5| into vaporizer and 'superheater chamber 52 at a point below the middle thereof, but some distance from the bottom thereof.

Molten sulfur is discharged into chamber 62 through a suitable distributing devic and contacts a hot moving bed of pelleted, granular or fragmentary refractory material which vaporizes the sulfur and superheats it to the-desired temperature. The superheated sulfur vapor leaves thetopof chamber 62 through lines 63 and '64.

superheated steam at a temperature of approximately 9.00-950 F. is introduced into the bottom of vaporizing and sup'erheating chamber 62 through valve-controlled line '55 'to purge the refractory material of sulfur. The sulfur vapor and steam leave the chamber 52 through line 65 and are returned tosul'fur melter 53. The sulfur condenses in melter 53 and the steam whollyor partially condenses to water at the sam time as thesolid sulfur is heated to the melting point. Only-sufficient superheatedsteam is admitted to the melter 53 through line 54 to supply heat in addition to that supplied through line fill-necesbucket, or any is withdrawn through valve-controlled pipe 11'.

After hopper 1| is filled with refractory material, valve 69 is closed andthe hopper is depressured by drawing off steam through valvecontrolled line 16. Valve I2 is then opened and the refractory material passes from hopper 'II through line 13 to the elevator I1. In this way refractory material is continuously withdrawn from chamber 62 through either hopperTI or hopper -14 and supplied continuously to the elevator 11.

Instead of purging sulfur from the refractory material by admitting superheated steam into the bottom of chamber 62, sulfur may be purged from the refractory material in hoppers H and 14, by admitting superheated steam into the bottom thereof through valve-controlled lines I9 and 80, respectively, and withdrawing the steam and sulfur vapors from the top of hoppers II and 14 through valve-controlled lines 8| and 82, respectively. From the line 8| the steam and sulfur vapors pass to line 66 and then to sulfur melter 53.

Refractory material is charged from the top of the elevator 11 through line 83 to kiln 84. Kiln 94 is heated by means of a mixture of air and combustible gas, liquid or powdered fuel introduced at spaced points through valve-controlled lines 85 and 86. Combustion gases are withdrawn from the kiln through valve-controlled lines 81, 80 and 89. If desired, combustion gases from the kiln may be circulated through the elevator TI and withdrawn from the top thereof through valve-controlled line 90 in order to preheat the refractory material before it is introduced into 7 the top of the kiln. If for example, the refractory material is heated to approximately 1400" F. in the kiln, it may be preheated to approximately 1200 F. in the elevator by circulating the flue gases therethrough. Heated refractory material leaves the bottom of the kiln 84 through either lines 9I or 92 controlled by valves 93 and 94, respectively. When refractory material I is discharged from the kiln through line 9| into hopper 95, valve 96 in the outlet 9'! of hopper 95 will be closed. Valve 94 in the inlet 92 to hopper 98 will be closed, and valves 99 in the outlet I of hopper 98 will open so that refractory material can flow from hopper 98 continuously into the top of the vaporizer and superheater 62. As soon as hopper 98 is empty, valve 99 and valve IOI in line I02 are closed and sulfur vapors are exhausted from' the hopper through valve-controlled line I03. Sulfur vapors exhausted through line I03 may be recycled before or after condensation to separator 51 by means of a line not shown.

After hopper 98 is depressured valve 94 is opened to permit hot refractory material to flow from kiln 84 into the hopper.

Hopper 95 is filled with hot refractory material during the period that refractory material is fed from hopper 98 into the chamber 62. After hopper 95 is filled, valve 99 is closed and hopper 95 is pressured with sulfur vapors through line I04, controlled by valve I65, connected to line 63. Hopper 95 is now ready to feed hot refractory material to chamber 62 by opening valve 96.

6 Hopper is exhausted of'sulfur vapor through valve' controlled line I06 when it is empty and the sulfur vapors may be recycled to separatoril. Hopper 98 is pressured by admitting sulfur vapors thereto through line I02 controlled by valve I0l after it is filled and valve 94 has been closed. 7

Flue gas may be'removed from the refractory material in hoppers 95 and 98 through valve-controlled lines I06 and I03, respectively, prior to repressuring with sulfur vapors. It will be understood inconnection with Figure 1 that the purging steam with contained sulfur vapors may beused to melt solid sulfur, as described in connection with Figure 2, and that sulfur melting in Figure-2 by means of the purging steam may be omitted and sulfur melted by extraneous heating means only. y

The "method and apparatus described and shown in connection with Figure 2 have the advantage over those described and shown in Figure l, in that in Figure 1 the temperature to which the refractory material can be heated is limited by the ability of the metal of which the elevator is constructed to withstand high temperatures. At the present time, materials available for such construction are capable of standing a maximum temperature of about 1200 F. with the result that the limit to which the refractory material can be heated is about 1200 F. and the temperature to which sulfur can be heated by means of the refractory material is somewhat below 1200 F.

The apparatus of Figure 2 is not limited as to temperature because the heating kiln follows the elevator. Therefore, much higher sulfur vapor temperatures can be attained in conjunction with the construction shown in Figure 2.

In both Figures 1 and 2 all parts which come in contact with hot sulfur vapors are preferably made of or lined with refractory material which is not substantially attacked by sulfur.

In both Figures 1 and 2 the flow rate of refractory material through the vaporizing and superheating chamber, and the quantity of sulfur charged is so regulated that the temperature of the refractory material leaving the bottom of the chamber is above the vaporizing temperature of sulfur at existing pressure.

As an example of an operation carried out in the apparatus shown in Figure 2, alundum, as the refractory, in the form of 6 to 10 mesh size fragments is heated to 1400" F. in the kiln 84 by the combustion of natural gas. The granular alundum moves continuously through the kiln and passes to either hopper 95 or 98 and therefrom as previously explained through chamber 62. Molten sulfur at a temperature of 270 F. is pumped continuously through line 6| to chamber 62 wherein on contacting the moving granular alundum it is vaporized and superheated to 1200 F. before leaving chamber 62 through lines 63 and 64. Molten sulfur is charged to 62 at the rate of 24.7 pounds of sulfur per hour and granular alundum passes through chamber 62 at the rate of 1 cubic foot per hour. Steam at 900 F. is introduced into chamber 62 through line 65. This steam amounts to about 3 per cent by weight of the sulfur charged to chamber 62. The temperature of the alundum particles leaving through the bottom of chamber 62 is 900 F.

What is claimed is:

1. A closed system for vaporizing sulfur comprising, a vaporizer resistant to sulfur vapor corrosion, a closed hopper above said vaporizer and connected to the top thereof by a valved conduit,

a closed hopper below said vaporizer and con- 7 nected to the bottom lthlBOf by a valved conduit, solid granular irefrac'tory heating material adapted 'to be circulated through said system, a heater "in said system, means for conveying granular material from said .last mentioned hopper to said .heater and from said heater to 'saidr'firstimentioned hopper, means for charging fresh sulfur to the lower portion of said vaporizer, aiconduit'for'withdrawin sulfur vapors from the upper sectionof-said vaporizer, means vfor equalizing pressure between said first mentioned hopper and :said vaporizer, a conduit connected to :the'bottomiof .said second mentioned hopper ini'order to inject steam therein, condensing means connected to the upper portion of said second mentioned hopper, settling means connected to said condensing means, means for separately withdrawing water and liquid sulfur from said-settling means and means for charging liquid sulfur from said settling means to the lower portion of said vaporizer.

2. 'A system in accordance with claim l'in which the condensing means comprises a chamber and 5 means for feeding 'to said chamber solid sulfur.

CHARLES A. PORTER. MILTON M. MARISIC.

REFERENCES CITED The following references .are of record in the file of this patent:

UNITED STATES PATENTS 

1. A CLOSED SYSTEM FOR VAPORIZING SULFUR COMPRISING, A VAPORIZER RESISTANT TO SULFUR VAPOR CORROSION, A CLOSED HOPPER ABOVE SAID VAPORIZER AND CONNECTED TO THE TOP THEREOF BY A VALVED CONDUIT, A CLOSED HOPPER BELOW SAID VAPORIZER AND CONNECTED TO THE BOTTOM THEREOF BY A VALVED CONDUIT, SOLID GRANULAR REFRACTORY HEATING MATERIAL ADAPTED TO BE CIRCULATED THROUGH SAID SYSTEM, A HEATER IN SAID SYSTEM, MEANS FOR CONVEYING GRANULAR MATERIAL FROM SAID LAST MENTIONED HOPPER TO SAID HEATER AND FROM SAID HEATER TO SAID FIRST MENTIONED HOPPER, MEANS FOR CHARGING FRESH SULFUR TO THE LOWER PORTION OF SAID VAPORIZER, A CONDUIT FOR WITHDRAWING SULFUR VAPORS FROM THE UPPER SECTION OF SAID VAPORIZER, MEANS FOR EQUALIZING PRESSURE BETWEEN SAID FIRST MENTIONED 